1. Field of the Invention
The present invention relates to a high-frequency coupler and a communication device, which are used for a communication apparatus used for performing large-capacity data transmission over a short distance by using a weak UWB communication scheme in which a high-frequency wideband is used. Especially, the present invention relates to a high-frequency coupler and a communication device, which can be incorporated in and used by a small device such as a handheld device and be fabricated in a small size and at a low price.
2. Description of the Related Art
Noncontact communication is widely used as a way of communicating value information such as authentication information and electronic money or the like. Recently, as a further application of noncontact communication, large-capacity data transmission such as downloading of moving images or music and streaming video or music has been considered.
As a close proximity wireless transfer technology applicable to high-speed communication, “TransferJet” (registered trademark) using a weak ultra-wideband (UWB) signal can be cited (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-99236 and URL: www.transferjet.org/en/index.html (as of Jun. 23, 2009)). The close proximity wireless transfer technology (TransferJet) is basically a scheme in which a signal is transmitted by using the coupling action of an induction electric field. A communication device which uses the close proximity wireless transfer technology includes a communication circuit section configured to perform high-frequency signal processing, a coupling electrode configured to be separately placed at a certain height from the ground, and a resonance section configured to efficiently supply a high-frequency signal to the coupling electrode. The coupling electrode or a component which includes the coupling electrode and the resonance section is also called a “high-frequency coupler” in the present specification.
The close proximity wireless transfer system can be configured as a pair of a reader/writer (initiator) used for transmitting a request command and a transponder (target) used for transmitting a reply command back, in the same way as near-field communication (NFC) of the related art (the NFC is standardized as ISO/IEC IS 18092).
The transponder end is supposed to be incorporated in and used by a small device such as a handheld device. Therefore, it is desirable to fabricate the high-frequency coupler in a small size and at a low price.